1. Field of the Invention:
This invention pertains to drilling rigs for use in drilling boreholes in the earth such as those drilled in the search for oil and gas.
2. Description of the Prior Art:
As is well known drilling derricks or rigs are used to drill holes in the earth in a search for oil and gas. The most common method is the rotary drilling method in which a bit is suspended at the lower end of a string of drill pipe and the drill pipe is rotated by a rotary table placed at the bottom of the derrick. Drilling fluid is circulated down through the drill pipe and up through the annulus between the drill pipe and the wall of the borehole to remove cuttings from the bottom of the hole as they are formed by the rotation of the bit. As the hole gets deeper, additional joints or sections of drill pipe has to be added. When additional joints are needed the joint is connected to the traveling block which is suspended inside the derrick. After entering through what is known as a V-door which is an opening in the side of the derrick, the joint of drill pipe is raised to a vertical position where it is connected to the drill pipe already in the well bore. This, of course, is repeated until the well is drilled to its required depth. Another type pipe is used to line the well bore and is commonly called casing. This casing likewise is added joint by joint and lowered into the well bore. The additional joints of drill pipe is commonly brought in through the same V-door as the drill pipe and is connected to the previous strings of casing and lowered in the same manner as discussed for the drill pipe. Many patents have issued on the drilling derrick and related equipment. One such patent is U.S. Pat. No. Re 29,541 which shows the pipe P mounted in a pipe storing rack 35 on the same side of the drilling derrick as is open forward access 33 which is provided for removing and placing drill pipe relative to the power swivel. Other patents which relate to the handling or racking of pipes and derricks includes U.S. Pat. No. 2,628,725; 4,274,778; 4,208,158; 4,117,941; 2,412,020; and 4,044,895. To the best of my knowledge in all of the prior derricks, none of the pipe racking means are located on 180.degree. from the V-door or the opening to which the drill pipe is to enter the derrick. The stored pipe is within the derrick such as shown in U.S. Pat. No. 2,412,020 where the stored pipe is within the frame of the derrick itself. This prior storage arrangement restricts the amount of drill pipe that can be racked. Also, when there is restriction in a working area such as when the pipe is stored at the same area as the V-door, then there is considerable restriction so that if one has a casing stored and is trying to enter drill pipe into the derrick there is considerable obstruction as one gets in the way of the other. This is certainly an awkward arrangement and is an operation which needs to be improved.